2001ApJ...561L.111J

Young stellar systems in the solar neighborhood provide valuable laboratories for detailed studies of star and planet formation. The bright F8 V star HD 199143 and the Li-rich late-type emission-line star HD 358623 are among the nearest young stars identified to date and may be members of a young association in Capricornus. We present high-resolution near-infrared images of these two sources, obtained using the adaptive optics system on the 3.6 m telescope at the European Southern Observatory in La Silla, Chile. Our observations reveal that both are, in fact, close binary systems. The newly discovered companion at a separation of ∼1" may account for the unusual characteristics of HD 199143–rapid rotation, emission lines, ultraviolet variability, and excess infrared emission–recently discussed by van den Ancker and coworkers. HD 199143 may be a rare example of a close binary with only a circumsecondary disk. With the detection of a ∼2" companion, HD 358623 is now possibly one of the closest known T Tauri binaries. Both binary systems are prime targets for follow-up spectroscopic and astrometric observations.